"Commissioning of Large Dams in the 20th Century, by Decade",

,Number of Dams
Before 1900, 630 
1900s, 353 
1910s, 601 
1920s, 809 
1930s, 964 
1940s, 913 
1950s," 2,735 "
1960s," 4,788 "
1970s," 5,418 "
1980s," 4,431 "
1990s," 2,069 "